1. Field of the Invention
The invention relates to an electrophotographic photoconductor to be used for image formation by an electrophotographic system, a method of producing the electrophotographic photoconductor and an image forming apparatus using the electrophotographic-photoconductor.
2. Description of the Related Art
Electrophotographic photoconductors which are used to form an image in an electrophotographic system and exposed to light corresponding to image information to thereby form an electrostatic latent image are used in image forming apparatuses. These image forming apparatuses provided with this electrophotographic photoconductor are widely utilized not only in copying machines but also in printers as output means used in, for example, computers for which there has been a significantly increased demand in recent years.
Generally, the electrophotographic photoconductor is formed by applying an organic light-sensitive layer to the outside peripheral surface of a hollow and cylindrical conductive support (base member) made of an conductive material. In many current electrophotographic photoconductors, the light-sensitive layer is designed to have a laminate structure in which an undercoat layer, a charge generation layer and a charge transport layer are applied and laminated in this order on a conductive support, to bring out a higher performance. Furthermore, there has been a proposal to improve the mechanical durability of an electrophotographic photoconductor by applying a surface protective layer as the outermost layer of a light-sensitive layer.
For a material of this surface protective layer, there are a proposal using a polycarbonate resin having a polar group (see, for example, Specification of U.S. Pat. No. 4,260,671) and a proposal using a polycarbonate resin having a fluorine-substituted alkyl group (see, for example, Publication of Japanese Patent No. 3246362).
Moreover, as the surface protective layer, one obtained by using a three-dimensional crosslinking siloxane resin is proposed (see, for example, ITAMI, SAKIMURA, OSHIBA and WATANABE, “Development of ultra-durable photoconductor (Mega OPC)”, KONIKA TECHNICAL REPORT, Konica Corporation, 2001, Vol. 14, p 43-46). When this surface protective layer is formed, a coating solution produced in a small amount is used only once to apply it by slide hopper system coating because the coating solution itself has reactivity and is short-lived. Also, in this method, a charge transport material having a specific molecular structure is used because usual charge transport materials used for a charge transport layer have the problem concerning solubility in an alcohol solvent and the formation of a uniform coating film.
As a method of forming the surface protective layer, a method is generally used in which a coating solution prepared by dissolving a resin and other components in a solvent is applied to a light-sensitive layer by a dip coating method, a roll coating method, spraying method, slide hopper method or ink jet method and the solvent is vaporized by hot air drying, natural drying or the like.
However, higher durability is required for current electrophotographic photoconductors to improve the durability of a machine body and process speed and for the adoption of a contact charge system and the current surface protective layer constituted of a resin dispersion film have come to be in the situation where it cannot cope with the requirement.
Therefore, in the method described in ITAMI et al., it is intended to improve the durability of the surface protective layer by applying a siloxane type monomer component which is a material for forming the surface protective layer and then by thermally curing the monomer component to form the surface protective layer having a firm three-dimensional crosslinking structure.
However, as a result of the studies made by the inventors of the present invention, it has been found that the method described in ITAMI et al., in which an initiator that polymerizes a monomer component is used in the formation of the surface protective layer, this initiator reaches a trap level when it remains in the surface protective layer and has an adverse influence on the electric properties of the layer. Some ideas occur, which include an idea that the amount of the initiator to be used is reduced and an idea that an additive that stabilizes potential characteristics is added. However, it has been also found that these measures reduce the strength of the film.
The inventors of the present invention have found that a specific amine compound is an effective compound as an initiator and also has the effect of stabilizing electric characteristics, and proposed in the previous patent application (Publication of JP-A No. 2005-338271) that this amine compound is used not as an initiator but as an additive in a light-sensitive layer.